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ideally.... hot steam cleaning.... followed by vapor degreasing... then baking out in an oven.....

but the real world only affords that thorough a cleaning usually to the places that weld cylinder heads and automotive aluminum every day... a lot of those castings are Very porous and have soaked up a lot of oil over the years... clean it best you can and bake or preheat the best you can... and expect guck to come out of the casting as you attempt to weld... it may take a few stabs at it before it burns out and you get a decent weld.... or maybe you will get lucky and it goes like a breeze..... but try to clean as thoroughly as you can before trying to weld....

hot pressure wash and engine cleaner should get most of the surface crud off...

how about some pics so we can better understand what you may be facing on warpage issues...and general setup as well as welding?? type of welder?? makes a difference... many times with an inverter like a Dynasty you can get in and get out without much heat being put into the surrounding area...

You should try to clean all manifold with soap(something that dissolves oli) and hot water. Try to clean it as good as possible inside out. The area you are going to weld clean with acetone. Before welding use stainless steel wire brush and wipe it again with acetone. Wipe the wire also with acetone.

Heating up the manifold will help to avoid little cracks when welding. If the weld cools too quickly, it can crack in the end.

As for wire i would use 4043(AlSi5)
I would also use thoriated (red) or lanthanated (gold) tungsten. That way you can keep the tungsten sharp and these don't contaminate so easily.

The manifold is for a supercharged motor but it's a little unusual since the SC sits directly on top of the motor but does not discharge down into the manifold but rather up then through an air-to-air innercooler at the front of the car then back to an inlet at the back of the intake manifold which is pancake style and I'm looking to extend the air charge opening as shown about 6" to make room for a larger plenum on the back of the supercharger just as is shown here. This guys used a mig/spool gun and laid in a ton of weld then cleaned it up but I'm not sure how it will hold up. I'll be using tig on a Syncrowave 180.

This is a "shadetree" type of project so no fancy steam or sonic cleaning unless I hire that stuff out but I've got the surface clean with degreaser, I can certainly get after it a bit more with some acetone or something once I get the cuts made where I'm looking to make changes.

I would like to make these welds without warping the flanges at either the heads or block. I have a parts motor I could bolt this to while welding if that would help it hold it's shape..

Sorry Brian
somehow I missed that... looks to me that you are gonna be pretty light on horsepower with a sync 180 on that much mass of aluminum... even with a bunch of preheat and maybe helium... 180amps is good for 3/16ths aluminum... and it looks like anyplace on that manifold is thicker by a bunch... plus you are probably looking at 15 or so pounds of aluminum heat sink...
am not trying to be a downer but you may be better off finding a buddy with a much larger machine... to tackle this...

free advice is worth what you pay for it...but this is how I see it... other opinions may disagree

Last edited by H80N; 11-29-2011 at 05:42 PM.
Reason: clarity..

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I've welded up to 3/8" aluminum flanges with my 180 but nothing as large as this manifold which has some areas that are 1/4" thick but most is about 1/8-3/16 and the actual flanges may be as much as 3/8"

Fortunately I have two of them so I can use one as a practice piece. I'm going to use a propane grill to bake it and an electric hot plate to maintain preheat as much as possible. If I can do it I'll be pushing my Sync 180 pretty hard.

Made some practice welds on the spare manifold this weekend. I cleaned it up, ground/sanded out the areas to be welded, baked it for an hour and sanded off the crud.

Made a bunch of test welds attaching some scrap pieces in 1/8" and 1/4". No problem with having enough power with my Syncrowave set at 150amps, I did not preheat. I did get a little bit of crud floating on the top of the puddle but not alot so I'm thinking I'll be fine with this setup.